The demand for rocket engines capable of carrying payloads to space or near-Earth orbits continues to grow. However, engines such as those used to launch satellites are costly to design and manufacture. Consequently, manufacturers of such rocket engines are constantly seeking new ways to reduce the design and manufacturing costs of producing rocket engine components.
One such component is the rocket thrust chamber within which the propellants of the rocket engine are combusted and accelerated. Because of the extremely high temperatures of the propellants moving through the thrust chamber, the walls of the thrust chamber must be cooled in those applications that require sustained engine firings. Such cooling is typically accomplished by flowing a coolant through tubes that form the inner wall of the thrust chamber. Since the manufacture of such thrust chambers is costly, novel ways of manufacturing such thrust chambers have been developed.
One method of manufacturing such a thrust chamber is to braze a plurality of cooling tubes together to form of tube bundle onto which molten metal is sprayed to form a structural jacket. This method requires that any gaps between adjacent cooling tubes have been properly brazed so when the process of spring the molten metal occurs, none of the molten metal is allowed to infiltrate into gaps between adjacent cooling tubes. Should such infiltration occur, those adjacent tubes could become bonded together so rigidly that they are unable to expand and contract to the extent necessary to accommodate the thermal expansion that occurs during normal operation of the rocket thrust chamber. This could result in a useful life of the rocket thrust chamber that is less than the intended design life thereof.
Unfortunately, the process of brazing tubes to form tube bundle is a complex process, the success of which is highly dependent upon the tolerances to which the individual tubes have been manufactured. Slight variations and tube shapes can result in anomalies during the brazing cycle, causing one or more gaps occur in a braze that is supposed to be continuous. Attempts at additional brazing cycles to eliminate such gaps often fail to seal these gaps, and may cause gaps to occur in brazes that were continuous after the first brazing cycle. In those cases where the gaps cannot be eliminated, the tube bundle must be discarded, and a new tube bundle must be fabricated. As those skilled in the art will readily appreciate, discarding tube bundles that include these gap anomalies increases the overall cost of manufacturing rocket thrust chambers, and therefore the cost of manufacturing rocket engines.
What is needed is a method of making a rocket thrust chamber from a tube bundle that has one or more gap anomalies in a braze that is supposed to be continuous.